Method of removing metal values from solution

ABSTRACT

THE PRESENT INVENTION RELATES TO NEW COMPOUNDS WHICH ARE GRAFFT COPOLYMERS OF CELLULOSE AND POLYACRYLTHIOAMIDE AND GRAFT COPOLYMERS OF SYNTHETIC POLYMERS AND POLYACRYLTHIOAMIDE WITH THE GENERAL FORMULA   (A)M-(CH2-CH(-C(=NH)-SH))N   WHEREIN A IS CELLULOSE OR A SYNTHETIC POLYMER, M IS THE DEGREE OF POLYMERIZATION OF CELLULOSE AND THE DEGREE OF POLYMERIZATION OF SUCH SYNTHETIC POLYMER RANGING FROM 150 TO 2,000, N IS THE DEGREE OF POLYMERIZATION OF POLYACRYLTHIOAMIDE RANGING FROM 400 TO 4,000, AS WELL AS TO A METHOD OF PRODUCING SAID NEW COMPOUNDS AND TO APPLICATION THEREOF. THE METHOD OF PRODUCING SAID COMPOUNDS RESIDES IN TREATING GRAFT COPOLYMERS OF CELLULOSE AND POLYACRYLONITRILE, OR GRAFT COPOLYMERS OF SYNTHETIC POLYMERS AND POLYACRYLONITRILE, WITH HYDROGEN SULPHIDE OR WITH SALTS OF HYDROSULPHURIC ACID IN AN AQUEOUS OR AN ORGANIC MEDIUM AT A TEMPERATURE OF 60-100*C. AND SUBSEQUENTLY ISOLATINGTHE TARGET PRODUCT. THE HEREIN-PROPOSED COMPOUNDS CAN FIND APPLICATION AS ELECTRON-EXCHANGE COMPLEX-FORMING MATERIALS IN CHEMICAL INDUSTRY, METALLURGY, AND IN OTHER INDUSTRIES.

United States Patent Moscow, U.S.S.R. N0 Drawing. Filed June 22, 1970,Ser. No. 48,518 Int. Cl. C22b 43/00, 11/04 U.S. Cl. 75-101 BE 11 ClaimsABSTRACT OF THE DISCLOSURE The present invention relates to newcompounds which are grafft copolymers of cellulose andpolyacrylthioamide and graft copolymers of synthetic polymers andpolyacrylthioamide with the general formula din-on).

i SH in wherein A is cellulose or a synthetic polymer,

m is the degree of polymerization of cellulose and the degree, ofpolymerization of such synthetic polymer ranging from 150 to 2,000,

n is the degree of polymerization of polyacrylthioamide ranging from 400to 4,000, as well as to a method of producing said new compounds and toapplication thereof.

The method of producing said compounds resides in treating graftcopolymers of cellulose and polyacrylonitrile, or graft copolymers ofsynthetic polymers and polyacrylonitrile, with hydrogen sulphide or withsalts of hydrosulphuric acid in an aqueous or an organic medium at atemperature of 60100 C. and subsequently isolating the target product.

' The herein-proposed compounds can find application aselectron-exchange complex-forming materials in chemical industry,metallurgy, and in other industries.

The present invention relates to new compounds which are graftcopolymers of cellulose and polyacrylthioamide and graft copolymers ofsynthetic polymers and polyacrylthioamide, to methods of theirproduction, and to ap plications thereof.

Said new compounds find application in the chemical industry forpurifying waste 'water from mercury ions, in metallurgy for selectiveextraction of ions of noble metals from industrial waste solutions, andin other branches of industry.

According to the invention, these new compounds, viz, graft copolymersof cellulose or of synthetic polymers and polyacrylthioamide, have thefollowing general formula:

2 (A)... Hz-C H) n I SH rlH wherein A is cellulose or a syntheticpolymer,

m is the degree of polymerization of the cellulose or the degree ofpolymerization of such synthetic polymer in the range of ISO-2,000,

3,728,103 Patented Apr. 17, 1973 ice n is the degree of polymerizationof polyacrylthioamide within 4004,000.

A graft copolymer of cellulose and polyacrylthioamide is a fibrousmaterial, fabric or powder, which is dark yellow in color, featureshydrophilic properties close to those (ii cellulose materials, and isstable to temperatures up to The molecular weight of the main chain is20,000- 3,000,000. The molecular weight of the side chain ofpolyacrylthioamide is 20,000-200,000.

Graft copolymers of synthetic polymers and polyacrylthioamide, such as agraft copolymer of polyvinyl alcohol and polyacrylthioamide, or a graftcopolymer of polycaproamide and polyacrylthioamide, or a graft copolymerof a polyolefine and polyacrylthioamide, and the like, have the form offibres, fabrics or granules whose color ranges from bright yellow todark yellow. These compounds are stable at temperatures within a rangeof from to C.

The molecular weight of the main chain of the graft copolymer ofpolyvinyl alcohol and polyacrylthioamide ranges from 80,000 to 150,000,that of the side chain, from 20,000 to 200,000.

The molecular weight of the main chain of the graft copolymer ofpolycaproamide and polyacrylthioamide ranges from 10,000 to 20,000, thatof the side chain, from 20,000 to 200,000.

The molecular weight of the graft copolymer of a polyolefine andpolyacrylthioamide ranges from 6,000 to 300,000, that of the side chain,from 20,000 to 200,000.

According to the invention, the method of producing said graftcopolymers of cellulose or synthetic polymers and polyacrylthioamideresides in that graft copolymers of cellulose or synthetic polymers andpolyacrylonitrile are treated With hydrogen sulphide or with salts ofhydrosulphuric acid in an aqueous or organic medium at a temperature of60-l00 C. with subsequent isolation of the final product.

The process is preferably carried out in an aqueous medium at a pH notover 8.

If the process is to be carried out in an aqueous medium, sodium andammonium sulphides and hydrosulphides should be preferably used as saltsof hydrosulphuric acid, whereas, in case the process is to be carriedout in an organic medium, preference should be given to ammoniumhydrosulphides.

It is preferable that dimethyl formamide, dioxane, or ethyl alcoholshould be used as an organic solvent.

The method proposed herein is effected as follows.

Graft copolymers of cellulose or synthetic polymers withpolyacrylonitrile, with the content of polyacrylonitrile therein rangingfrom 10 to 70 Weight percent, are reacted with hydrogen sulphide or withsalts of hydrosulphuric acid. The process is carried out at atemperature of 60l00 C.

This process can be carried out either in an aqueous or in an organicmedium. As an organic solvent use can be made of dimethyl formamide,dimethyl sulphoxide, dimethyl acetamide, ethylene carbonate, dioxane,alcohols, and other solvents. It is preferable to use dimethylformamide, dioxane, or ethyl alcohol for this purpose.

It is likewise preferable that sodium or ammonium sulphides andhydrosulphides be used as salts of hydrosulphuric acid.

When carrying out the process in an aqueous medium, it is desirable thatthe pH value should not exceed 8. This is achieved by adding a phosphatebuffer (monobasic sodium or potassium phosphate). The duration of theprocess is 2-10 hours. The resulting final product features a sulphurcontent of 3 to 29 Wt. percent, electron-exchange capacity of from 1 to9 meq./ g. and degree of conversion of nitrile groups to thioamidegroups of 20 to 80%.

When the final product is heated with a 0.5 N solution of sulphuric acidat 100 over a period of 4 hrs., its sulphur content andelectron-exchange capacity do not change. When the final product isheated with a 0.5 N solution of caustic soda at 100 C. over a period of4 hrs., its sulphur content and electron-exchange capacity becomediminished by 5 to 25%.

The obtained products are resistant to air oxidation and can withstandprolonged storage in the open air without preliminary reduction thereofprior to utilization.

The present method alows the use as stock materials of waste productsresulting in the production of synthetic fibres, films, plastics andpolymers, which do not comply with the adopted standards and cannot beemployed for the purpose they have been initially produced. According tothe herein-proposed method the target products can be obtained in theform of fibres, fabrics, films, nonwovens, powders and granules, whichfact makes it possible to broaden the range of their application andthat of the equipment involved.

Graft copolymers of cellulose or synthetic polymers andpolyacrylthioamide produced by the present method featureelectron-exchange and complex-forming properties and, according to theinvention, are employed as electronexchange complex-forming materials,for example, for purifying industrial waste solutions from mercury ions.

This process is efiected by filtering industrial waste solutions thatcontain mercury ions at a concentration of 5-100 mg./1. by passing themthrough the hereinproposed electron-exchange complex-forming material ata temperature of 20-95 C. and a pH of 5-7. The material efiects completesorption of the mercury ions. Mercury is recovered by burning the fibresof the graft copolymer employed and subsequent condensation of mercuryvapors.

The application of said materials enables substantial purification ofindustrial waste solutions (the residual amount of mercury therein notexceeding 0.005 trig/1.).

Said electron-exchange complex-forming materials are also applicable forselective removal of noble metals from industrial solutions, the contentof noble metals therein being from 0.001 to g./l. and that ofnon-ferrous metals, from 1 to 300 g./l.

The process is effected by passing such solutions through an adsorbingcolumn filled with the ion-exchange complex-forming material, eitherwith heating to 90-95 C., or at room temperature.

The material with chemically bound metal is separated by filtration,washed with water, dried and calcined at 700 C., with the obtaining ofthe metals in the form of a powder.

For separating platinum and palladium from iridium, rhodium andruthenium, the initial solution is passed through an adsorbing column atroom temperature, whereby platinum and palladium are subjected tosorption, whereupon the resulting filtrate is passed through the nextadsorbing column at a temperature of 90-95 C. with the collection ofiridium, rhodium and ruthenium. This method allows complete removal ofnoble metals, which effect cannot be achieved by using the now-existingmethods (such as carbonization, extraction with organic solvents, etc.).I

For a better understanding of the present method of producing graftcopolymers of cellulose or of synthetic polymers and polyacrylthioamidethe following examples are given hereinbelow by way of illustration.

EXAMPLE 1 g. of a graft copolymer of cellulose and polyacrylonitrile (inthe form of a fibre or fabric) which contains 22 wt. percent of graftpolyacrylonitrile (5.8 wt. percent of nitrogen) is treated over a periodof 6 hrs. in a 4 hermetically sealed apparatus at a temperature of C.with 600 ml. of a 45% aqueous solution of hydrogen fllglphide. The finalproduct is washed with water and ied.

The target product features a sulphur content of 3.45 wt. percent, anelectron-exchange capacity of 1.1 meq./g. (for Ag and degree ofconversion of nitrile roups to thioamide groups amounting to 26% oftheoretical.

EXAMPLE 2 20 g. of a graft copolymer of cellulose and polyacrylonitrilein the form of fibre or fabric, comprising 35 wt. percent of graftpolyacrylonitrile (9.2 wt. percent of nitrogen), are treated during 6hrs., in a hermetically sealed apparatus at a temperature of C. with 600ml. of a 3.6% solution of hydrogen sulphite in dimethyl formamide. Thenthe fibre is washed with water and dried. The target product features asulphur content of 14.6 wt. percent, an electron-exchange capacity of4.5 me'q./ g. (for Ag*') and a degree of conversion of nitrile groups tothioamide groups equal to 70% of theoretical.

EXAMPLE 3 20 g. of a graft copolymer of cellulose and polyacrylonitrile,containing 50 wt. percent of graft polyacrylonitrile (13.2 wt. percentof nitrogen) are treated with 600 ml. of a 6% aqueous solution of sodiumsulphide at a pH of 7.5-8 during 4 hrs. at a temperature of 80 C. in ahermetically sealed apparatus. For maintaining the pH value at 7.5-8, aphosphate buifer (monobasic sodium phosphate) is added to the reactionmixture.

The obtained product is washed with water and dried. The productcontains 11.82 wt. percent of sulphur, its electron-exchange capacity is3.5-3.7 meq./ g. (for Ag), and the degree of conversion of nitrilegroups to thioamide groups is 64.1% of theoretical.

EXAMPLE 4 EXAMPLE 5 20 g. of a graft copolymer of polycaproamide andpolyacrylonitrile, containing 52.4 wt. percent of graftpolyacrylonitrile, are treated with 600 ml. of a 30% aqueous solution ofammonium hydrosulphide in a hermetically sealed apparatus at 70 C.during 3 hrs.

The obtained product is washed with water and dried.

Sulphur content is 6.9 wt. percent, electron-exchange capacity, 3.05meq./g. (for Ag+).

Degree of conversion of nitrile groups to thioamide groups is 39.4% oftheoretical.

EXAMPLE 6 20 g. of a graft copolymer of polyethylene andpolyacrylonitrile; containing'36.3 wt. percent of graftpolyacrylonitrile are treated with 600 ml. of a 10% aqueous solution ofsodium sulphide in the presence of a phosphate buffer which is monobasicsodium phosphate (pI-I =7.5-8) at a temperature of 70 C. during 4 hrs.

The obtained product is washed with water and dried.

Sulphur content is 3.67 wt., percent electron-exchange capacity of theproduct '(for Ag is 2.14 meqJg.

Degree of conversion of nitrile groups to thioamide groups is 13.5% oftheoretical.

EXAMPLE 7 EXAMPLE 8 A solution comprising g./l. of silver nitrate, 0.1g./l. of ferric nitrate, 40 g./l. of cupric nitrate, 0.001 g./l. of zincnitrate and 0.015 g./ l. of aluminum nitrate is passed through a columncontaining 100 g. of the electronexchange complex-forming materialobtained as described in Examples 1-7 at a rate of 500 mL/hr. at roomtemperature. The filtrate comprises:

G./1. FC(N 3)3 0.1 Al(N 3)3 0.015 Cl1(NO 39 Z11(N 3) 3 0.001

EXAMPLE 9 G./l. Ir 0.0034 Au 0.005 Cu 4.7 Rh 0.026 Co 10.5 Ru 0.001 Ni6.0 Fe 1.5

EXAMPLE 10 A chloride solution comprising 2.21 g./l. of platinum, 6.257g./l. of palladium, 0.019 g./l. of iridium, 0.771 mg./l. of rhodium,0.152 g./l. of ruthenium, 0.098 g./l. of gold, 10.5 g./l. of cobalt, 6.0g./l. of nickel, 1.5 g./l of iron and 5 g./l. of copper, is heatedduring 2 hrs. with 5 g. of the complex-forming electron-exchangematerial obtaiged as described in Examples 1-3, at a temperature of 10C.

Said material with the adsorbed metals is filtered, dried and burned.

The filtrate comprises:

G./l. Co 10.5 Ni 6 Fe 1.5 Cu 4.7

The residue after the burning comprises 99.8 wt. percent of metals fromthe group of platinum and gold and 0.2 wt. percent of ash.

EXAMPLE 11 A sulphate solution comprising 0.0031 g./l. of platinum,0.0038 g./l. of palladium, 0.0708 g./l. of iridium, 0.0040 g./l. ofrhodium, 0.059 g./1. of ruthenium, 1 g./l. of gold,

-g./l.-of nickel, 20 g./l. of iron and 0.5 g./l. of copper is heatedwith 5 g. of the complex-forming electronexchange material obtained asdescribed in Examples 1, 3, 5, in an autoclave during 2 hours at atemperature of C. with 40 g./l. of NaCl.

Said material is filtered, dried and burned.

The filtrate comprises:

G./l. Pt 0.0002 Rh 0.0001 Ni 90 Pd 0.0001 Ru 0.0003 Fe 20 Ir 0.0003 Au0.00001 Cu 0.49

After burning a powder is obtained, comprising 99.8 wt. percent ofmetals from the group of platinum and gold and 0.2 wt. percent of ash.

EXAMPLE 12 An aqueous solution, comprising water-soluble compounds ofmercury (50 mg./l.) at pI-I-=5, is filtered through a column containing5 g. of the complex-forming electron-exchange material obtained asdescribed in Examples 1-7, at a temperature of 20 C. at a rate of 1000mg. per hour. The filtrate contains no mercury.

What is claimed is:

1. A method of removing chemically bound metals from a solution, saidmethod comprising passing a solution containing chemically bound metalswhich are to be removed therefrom through an adsorbing column containinga graft copolymer of polyacrylthioamide and cellulose or syntheticpolymers of the general formula wherein A is cellulose or a syntheticpolymer,

In is the degree of polymerization of the cellulose U1 synthetic polymerand is between 'and 2,000, and

n is the degree of polymerization of polyacrylthioamide and is between400 and 4,000.

2. A method as claimed in claim 1 comprising separating the metal fromthe graft copolymer.

3. A method as claimed in claim 1 wherein the solution is an industrialwaste solution and the removed metal is mercury contained in thesolution in an amount between 5-100 mg./l.

4. A method as claimed in claim 3 wherein said waste solution is passedthrough the adsorbing column at a temperature of 20-95 C. and a pH of5-7.

5. A method as claimed in claim 4 comprising separating the mercury fromthe graft copolymer by burning said graft copolymer and condensing theresulting vapors.

6. A method as claimed in claim 1 wherein the metals removed from thesolution are noble metals in a concentration of 0.001 to 10 g./l.

7. A method as claimed in claim 6 wherein said solution is passedthrough the adsorbing column at a temperature of 20-95 C.

8. A method as claimed in claim 7 comprising separating the metal bydrying and calcining the graft copolymer with the adsorbed metal.

9. A method as claimed in claim 1 wherein the synthetic polymer ispolyvinyl alcohol, polycaproamide, or polyolefin.

10. A method as claimed in claim 1 wherein said solu- 8 tion is anaqueous solution with a pH of under about 8. 3,484,235 12/1969 Goss eta1. 75-121 11. A method as claimed in claim 1 wherein said solu-3,473,921 10/1969 Schmuckler 75-118 tion is an organic solution. FOREIGNPATENTS References Cited 5 938,880 10/1963 Great Britain 75-101 BEUNITED STATES PATENTS GEORGE T. OZAKI, Primary Examiner 3,484,39012/1969 Bauman et a1. 260-22 3,476,552 11/1969 Parks et a1. 75-101 RU.S. C1. X.R. 3,088,798 5/1963 Fetscher 75-101 BE UX 10 75-117, 118, 1213,458,476 7/1969 Bayer 75-118 X 3,481,904 12/1969 Bayer 75-118 X

